Transcript Chapter 19 Communities & Ecosystems (General Biology)

CHAPTER 19 – Communities and
Ecosystems
KEY PROPERTIES OF COMMUNITIES
• A community
– Is an assemblage of species living close enough
together for potential interaction..
1. Diversity
• The diversity of a community is the variety
of different kinds of organisms that make
up the community
There are two main components:
– Species richness, the total number of different
species in the community
– Relative abundance of the different species..
2. Prevalent Form of Vegetation
• The prevalent form of vegetation mainly
depends on the terrestrial situation
• The types and structural features of plants
in a community largely determine the kinds
of animals that live in the community..
3. Stability
• Community stability - ability to resist
change and return to its original species
combination after being disturbed
– Depends on both the type of community and
the nature of disturbances..
4. Trophic Structure
• The trophic structure of a community
concerns the feeding relationships among
the various species making up the
community..
Figure 19.4
INTERSPECIFIC INTERACTIONS IN
COMMUNITIES
•
Interspecific interactions are interactions
between species
1. Competition between species
2. Predation
3. Symbiosis
1. Competition Between Species
• Interspecific competition
– May occur when two or more species in a
community rely on similar limiting resources
– May limit population growth of the competing
species..
Competitive Exclusion Principle
• Russian ecologist G. F. Gause studied the
effects of interspecific competition in two
closely related species of protists..
Separate
cultures
Combined
cultures
P. aurelia
P. caudatum
Figure 19.5
• From his research, Gause concluded that
two species so similar that they compete
for the same limiting resources cannot
coexist in the same place
– Competitive Exclusion Principle..
• Testing the competitive exclusion
principle..
High
tide
Chthamalus
Balanus
Ocean
Low
tide
Figure 19.6
The Ecological Niche
• A species’ ecological niche
– Is the sum total of a species’ use of the biotic
and abiotic resources in its environment
– Is the species’ ecological role
Two species cannot coexist in a community if
their niches are identical..
Resource Partitioning
• Is the differentiation of niches that enables
similar species to coexist in a community
• There are two possible outcomes of
competition between species with identical
niches
– Extinction of one species
– Evolution of one species to use a different set
of resources..
A. ricordii
A. ricordii
A. distichus
A. insolitus
A. aliniger
A. christophei
A. distichus A. distichus
A. christophei
A. cybotes
A. cybotes
A. etheridgei A. etheridgei
A. insolitus
Figure 19.7
2. Predation
– Is when organisms eat other organisms
– Identifies the predator as the consumer and the
food species as the prey
– Includes herbivory, the consumption of plants
by animals..
Predator Adaptations
• Most predators have acute senses
• Many predators
– Have adaptations such as claws, teeth, fangs,
stingers, or poison to help catch and subdue
prey
– Are fast and agile..
Plant Defenses Against
Herbivores
• Plants have various types of defenses
against herbivores
– Chemical toxins
– Spines and thorns..
Animal Defenses Against
Predators
• Animals can avoid being eaten
– By using passive defenses such as hiding
– By using active defenses such as escaping or
defending themselves..
• Behavioral defenses include
– Alarm calls
– Mobbing..
Figure 19.8
• Distraction displays
– Direct the attention of the predator away from a
vulnerable prey to another prey that is more
likely to escape..
Figure 19.9
• Camouflage, or cryptic coloration
– Is a passive defense that makes a potential
prey difficult to spot against its background..
Figure 19.10
Some animals have mechanical or chemical
defenses against predators..
• Animals with
chemical defenses
are often brightly
colored
– This is a caution to
predators called
warning coloration..
Figure 19.11
• Mimicry
– Is a “copycat” adaptation in which one species
mimics the appearance of another
– Is used by some species to gain protection..
– A palatable or harmless species mimics an
unpalatable or harmful model..
Figure 19.12
– Two or more unpalatable species resemble
each other..
Figure 19.13
Predation and Species Diversity in
Communities
• Predator-prey relationships
– Can actually preserve species diversity..
• The experiments of Robert Paine
– Removed a dominant predator from a
community
– Provided evidence of the phenomenon of
predation..
With Pisaster
(control)
Without
Pisaster
Figure 19.14
• Paine’s experiments and others
– Led to the concept of keystone predators
• Keystone predators
– Help maintain species diversity by preventing
competitive exclusion of weaker competitors..
3. Symbiotic Relationships
• Is an interspecific interaction in which one
species, the symbiont, lives in or on another
species, the host
– Parasitism
– Mutualism
Parasitism
• Parasitism
– Is a symbiotic relationship in which one
organism benefits while the other is harmed
– The parasite obtains its nutrients by living in or
on its host organism..
Mutualism
– Is a symbiosis that benefits both partners
• Many mutualistic relationships have evolved from
predator-prey or host-parasite interactions..
The Complexity of Community
Networks
• The branching of interactions between species
makes communities complex..
Recruitment
Release of volatile
attractants
Chemical
in saliva
Wounding
Detection
by plant
Figure 19.17
DISTURBANCE OF COMMUNITIES
– Are episodes that damage biological
communities, at least temporarily
– Destroy organisms and alter the availability of
resources
– Affect all communities..
Ecological Succession
– Is the process of community change
• Primary succession
• Secondary succession..
• In primary succession
– A community arises in a virtually lifeless area
with no soil..
Barren landscape
Moss & lichens
Retreating glacier
• Primary succession from barren soil to a
complex community can take hundreds of
years..
Shrubs & small
trees
Larger, intermediate
species
Climax community
• Secondary succession occurs where a
disturbance has destroyed an existing
community but left the soil intact..
AN OVERVIEW OF ECOSYSTEM
DYNAMICS
• An ecosystem
– Is a biological community and the abiotic factors
with which the community interacts..
• Energy Flow
– Is the passage of energy through the
components of the ecosystem
• Chemical cycling
– Is the use and reuse of chemical elements
within the ecosystem..
• Energy
– Flows through
an ecosystem
when
consumers feed
on producers
– Cannot be
recycled within
an ecosystem,
but must flow
through
continuously..
Chemical cycling
(C, N, etc.)
Light
energy
Chemical
energy
Heat
energy
Figure 19.20
• Energy flow and chemical cycling
– Depend on the transfer of substances in the
feeding relationships, or trophic structure of an
ecosystem
• Trophic levels
– Divide the species of an ecosystem based on
their main sources of nutrition
• Trophic relationships
– Determine an ecosystem’s routes of energy
flow and chemical cycling..
Trophic Levels and Food Chains
• A food chain
– Is the sequence
of food transfer
from trophic level
to trophic level
– May have many
levels..
Quaternary
consumers
Carnivore
Carnivore
Tertiary
consumers
Carnivore
Carnivore
Secondary
consumers
Carnivore
Carnivore
Primary
consumers
Zooplankton
Herbivore
Producers
Plant
Figure 19.21
A terrestrial food chain
Phytoplankton
A marine food chain
• Herbivores, which eat plants, algae, or
autotrophic bacteria, are the primary consumers
of an ecosystem
• Above the primary consumers, the trophic levels
are made up of carnivores, which eat the
consumers from the levels below
– Secondary consumers include many small
mammals, such as rodents, and small fishes
that eat zooplankton
– Tertiary consumers, such as snakes, eat mice
and other secondary consumers
– Quaternary consumers include hawks and killer
whales..
• Detritivores, or decomposers
– Derive their energy from the dead material left
by all trophic levels
– Recycle the nutrients locked in organisms..
Figure 19.22
Food Webs
• The feeding relationships in an ecosystem
– Are typically not as simple as in an unbranched
food chain
– Are usually woven into complex food webs..
Quaternary,
tertiary, &
secondary
consumers
Tertiary
&
secondary
consumers
Secondary
&
primary
consumers
Primary
consumers
Producers
(plants)
ENERGY FLOW IN ECOSYSTEMS
• Food chains cannot be longer than 4 – 5
trophic levels.
– What limits food chains?
Productivity and the Energy
Budgets of Ecosystems
• Biomass
– Is the amount of organic material in an
ecosystem
• An ecosystem’s primary productivity
– Is the rate at which plants and other producers
build biomass..
• Productivity of different ecosystems..
Open ocean
Continental shelf
Extreme desert, rock, sand, ice
Desert and semidesert scrub
Tropical rain forest
Savanna
Cultivated land
Boreal forest (taiga)
Temperate grassland
Woodland and shrubland
Tundra
Tropical seasonal forest
Temperate deciduous forest
Temperate evergreen forest
Swamp and marsh
Lake and stream
Estuary
Algal beds and reeds
Upwelling zones
(a)Percentage of Earth’s
surface area
(b) Average net
primary
productivity
(g/m2/yr)
(c) Percentage of
Earth’s net
primary
productivity
Energy Pyramids
• When energy flows as organic matter
through the trophic levels of an
ecosystem, much of it is lost at each link in
a food chain..
Plant material eaten
by caterpillar
100 kilocalories (kcal)
35 kcal
Cellular
respiration
50 kcal
Feces
15 kcal
Growth
Figure 19.25
• An energy pyramid
– Is a diagram that represents the cumulative loss
of energy from a food chain..
Tertiary
consumers
10 kcal
Secondary
consumers
100 kcal
Primary
consumers
Producers
1,000 kcal
10,000 kcal
Figure 19.26
CHEMICAL CYCLING IN
ECOSYSTEMS
• Ecosystems
– Depend on a recycling of chemical elements..
The General Scheme of Chemical
Cycling
• Biogeochemical cycles
– Are chemical cycles in an ecosystem that
involve both biotic and abiotic components..
• Three key points to biogeochemical cycles
– Each circuit has an abiotic reservoir
– A portion of chemical cycling can rely
completely on geological processes
– Some chemicals require processing before they
are available as inorganic nutrients..
Consumers
• Generalized
scheme for
biogeochemical
cycles..
Producers
Detritivores
Nutrients
available to
producers
Abiotic
reservoir
Geologic
processes
Examples of Biogeochemical
Cycles
• A chemical’s specific route through an
ecosystem varies with the particular
element and the trophic structure of the
ecosystem..
The carbon cycle
CO2 in
atmosphere
Photosynthesis
Burning
Producers
Wood and
fossil fuels
Cellular respiration
Higher-level
consumers
Primary
consumers
Decomposition
Detritivores
Detritus
Figure 19.29a
The nitrogen cycle
Nitrogen (N2)
in
atmosphere
Detritus
Amino
acids and
proteins in
plants and
animals
Denitrifying
bacteria
Detritivores
Assimilation
by plants
Nitrates
(NO3– )
Decomposition
Nitrogenfixing bacteria
in root
nodules of
legumes
Nitrogen
fixation
Nitrifying
bacteria
Ammonium
(NH4+ )
Nitrogenfixing
bacteria
in soil
The phosphorous cycle
Uplifting
of rock
Phosphates
in rock
Weathering
of rock
Phosphates
in organic
compounds
Consumers
Producers
Phosphates
in soil
(inorganic)
Rock
Precipitated
(solid)
phosphates
Phosphates
in solution
Detritus
Detritivores
in soil
Figure 19.29c
The water cycle
Net movement of
water vapor by
wind (36)
Solar heat
Water vapor
over the sea
Precipitation
over the sea
(283)
Water vapor
over the
land
Evaporation and
transpiration (59)
Precipitation
over the land
(95)
Evaporation
from the sea
(319)
Surface
water and
groundwater
Oceans
Flow of water
from land to sea
(36)
Figure 19.29d
BIOMES
– Are the major types of ecosystems that cover
large geographic regions of the Earth..
How Climate Affects Biome Distribution
• Because of its curvature, Earth receives an
uneven distribution of solar energy.
Low angle of incoming sunlight
Sunlight directly overhead
Low angle of incoming
sunlight
Atmosphere
Figure 19.30
• The uneven heating causes rain and wind
– Heated by the direct rays of the sun, air at the
equator rises, then cools, forms clouds, and
drops rain..
Cloud formation
and rain
Descending
dry air
Temperate
zone
Ascending
moist air
releases
moisture
Tropics
Descending
dry air
Temperate
zone
• Proximity to large bodies of water and the
presence of landforms such as mountain
ranges also affect climate..
East
Wind
direction
Pacific
Ocean
Cascade
Range
Coast
Range
Figure 19.32
Terrestrial Biomes
• The distribution of terrestrial biomes
depends largely on climate
• If the climate in two geographically separate
areas is similar, the same type of biome
may occur in them..
• Most biomes are named for major physical or climatic
features and for their predominant vegetation..
Figure 19.33
• Tropical
forest..
Figure 19.34a
• Savanna
Figure 19.34b
• Desert
Figure 19.34c
• Chaparral
Figure 19.34d
• Temperate
grassland
Figure 19.34e
• Temperate
deciduous
forest
Figure 19.31f
• Coniferous
forest
Figure 19.34g
• Tundra
Figure 19.34h
Freshwater Biomes
• Aquatic biomes
– Occupy the largest part of the biosphere..
Lakes and Ponds
• Standing bodies of water - range from
small ponds to large lakes..
Figure 19.35a
In lakes and large ponds the communities are
distributed according to the depth of water
and its distance from shore.
• The photic (photosynthetic) zone
– Includes the shallow water near shore and the
upper stratum of water away from shore
– Is named because light is available for
photosynthesis
• The aphotic zone
– Is deeper, where light levels are too low to
support photosynthesis
• The benthic zone
– Is the bottom of all aquatic biomes
Rivers and Streams
– Are bodies of water flowing in one direction
– Support quite different communities of
organisms than lakes and ponds
Figure 19.35b
• Marshes, ponds, and other wetlands
– Are common in downstream areas
Figure 19.35c
• Human
activities have
affected many
streams and
rivers
Figure 19.36
Marine Biomes
• Oceans
– Cover about 75% of the planet’s surface
• Estuaries
– Are areas where a freshwater stream or river
merges with the ocean
– Are one of the
most biologically
productive
environments
on Earth
• “Nurseries of the
sea”..
Major Oceanic Zones
• Marine life is distributed according to
– Depth of the water
– Degree of light penetration
– Distance from shore
– Open water versus bottom..
• Oceanic zones
Intertidal zone
Continental shelf
Photic
zone
Pelagic
zone
Benthic zone
(seafloor)
Aphotic
zone
Figure 19.38
• The intertidal zone
– Is the area where land meets water
– Includes organisms adapted to attach to rocks
or vegetation or to burrow..
Figure 19.39
• The pelagic zone
– Is the open ocean
– Contains phytoplankton and zooplankton
• Plankton are organisms that are pushed around
because they are too small to resist the ocean
currents..
• The benthic zone
– Is the ocean bottom or seafloor
• Temperature is constant 4o C
– May include hydrothermal vent communities..
Figure 19.40